rem quick rename *.avi to *.vi in subfolder of current folder
rem usage: 
rem copy this bat to the folder you want to rename
rem then edit this file, say you want *.avi->*.vi
rem then save and double click quickren.bat
rem /r means recursive in all sub folders
rem this search all sub folder for *.avi and rename to *.vi
rem in cmd you can type: for /r %i in (*.avi) do rename %i *.vi

@echo off
rem cd c:\myvideos\secrets
for /r %%i in (*.txt) do rename "%%i" *.tx

rem if you want to use quickren.bat avi vi, try below instead
rem for /r %%i in (*.%1) do rename "%%i" *.%2